migration: Add a new option to enable only-migratable

Add a new option "--only-migratable" in qemu which will allow to add
only those devices which will not fail qemu after migration. Devices
set with the flag 'unmigratable' cannot be added when this option will
be used.

Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
Message-Id: <1484566314-3987-3-git-send-email-ashijeetacharya@gmail.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

include/migration/migration.h

@@ -38,6 +38,9 @@
 #define QEMU_VM_COMMAND              0x08
 #define QEMU_VM_SECTION_FOOTER       0x7e
 
+/* for vl.c */
+extern int only_migratable;
+
 struct MigrationParams {
     bool blk;
     bool shared;

qemu-options.hx

@@ -3585,6 +3585,15 @@ be used to change settings (such as migration parameters) prior to issuing
 the migrate_incoming to allow the migration to begin.
 ETEXI
 
+DEF("only-migratable", 0, QEMU_OPTION_only_migratable, \
+    "-only-migratable     allow only migratable devices\n", QEMU_ARCH_ALL)
+STEXI
+@item -only-migratable
+@findex -only-migratable
+Only allow migratable devices. Devices will not be allowed to enter an
+unmigratable state.
+ETEXI
+
 DEF("nodefaults", 0, QEMU_OPTION_nodefaults, \
     "-nodefaults     don't create default devices\n", QEMU_ARCH_ALL)
 STEXI

vl.c

@@ -182,6 +182,7 @@ bool boot_strict;
 uint8_t *boot_splash_filedata;
 size_t boot_splash_filedata_size;
 uint8_t qemu_extra_params_fw[2];
+int only_migratable; /* turn it off unless user states otherwise */
 
 int icount_align_option;
 
@@ -3884,6 +3885,9 @@ int main(int argc, char **argv, char **envp)
                 }
                 incoming = optarg;
                 break;
+            case QEMU_OPTION_only_migratable:
+                only_migratable = 1;
+                break;
             case QEMU_OPTION_nodefaults:
                 has_defaults = 0;
                 break;